This invention relates to soft contact lenses made of thermally annealed polyvinyl alcohol.
In general, existing aqueous swollen soft contact lens materials based in polymers of HEMA, also known as hydroxyethyl methacrylate or as ethylene glycol monomethacrylate, suffer from either weak mechanical strength, low dissolved oxygen permeability or a combination of both. Moreover, aqueous swollen soft contact lenses of crosslinked HEMA with one or more optional comonomers are known, as described in U.S. Pat. Nos. 2,976,576, 3,841,985 and 3,985,697. Such hydrogel polymers also suffer from either weak mechanical strength, insufficient dissolved oxygen permeability or a combination thereof. Efforts to increase oxygen permeability by increasing the water content of the hydrogels result in a further decline in the mechanical strength of the lens material to such an extent that they are extremely fragile.
Also, a polyvinyl alcohol crosslinked with glyoxal has been proposed as a contact lens material in U.S. Pat. No. 3,408,429. However, no disclosure of polyvinyl alcohol molecular weight, and no specifics concerning the amount of water present in the crosslinking step are disclosed. Additionally, there is no disclosure of annealing under crystallinity promoting conditions.
Furthermore, polyvinyl alcohol films and gels have been reported as opthalmic inserts in the lower conjunctival sac when imbibed with antibiotics such as tetracycline, pilocarpine, atropine and the like. Such materials are either in the form of a crosslinked film or as a water soluble viscous solution or gel. See, for example, Y. F. Maichuk, Ophthalmic Drug Inserts, Invest. Ophthalmol., Vol. 14, pages 87-90 (1975); D. W. Lamberts, Solid Delivery Devices, Int. Ophthalmol. Clinic, Vol. 20, No. 3, pages 68-69 (1980) and Y. F. Maichuk, Antibiotik, Vol. 12, No. 4, pages 43 2-5 (1967).
Further, the crosslinking of polyvinyl to form a borate crosslinked polyvinyl alcohol contact lens alcohol with a borate is disclosed in Applicant's copending U.S. application Ser. No. 308,742, filed Oct. 5, 1981, and now abandoned, the disclosure of which is hereby incorporated by reference in toto.
It is an object of the present invention to provide soft contact lenses obviating or substantially reducing the aforementioned drawbacks associated with the prior art.
It is a further object of the present invention to provide soft contact lenses comprising polyvinyl alcohol which has been annealed under crystallinity promoting conditions such that the annealed aqueous swollen lenses are substantially insoluble in the ocular tear environment, possess a high water content, an oxygen transmissibility in excess of that necessary to meet the needs of the human cornea, improved hot water resistance and superior mechanical properties.
It is a further object of the invention to provide, simple, low cost processes for the preparation of such lenses.
It is a further object of the invention to provide a method of correcting vision in patients in need of the same by wearing such a lens on the surface of the cornea.
It is a further object of the invention to provide a method of cosmetic enhancement of the eye of a patient by wearing such a lens, which has been suitably tinted to simulate the iris of desired color, on the surface of the cornea.